1. Field of the Invention
The present invention relates generally to impact tools, and more particularly to self-contained impact tools utilizing a combustible mixture to provide the energy necessary to accomplish work, either in a single operation or semi-automatic operation.
2. Description of the Prior Art
Impact tools are per se well known and have been utilized for a great number of purposes including loosening and tightening rotary fasteners such as nuts and bolts, setting rivets, and driving nails and staples. Basically, since the tools are generally portable and, accordingly, relatively lightweight, operation is predicated upon the transfer of a great amount of energy over a very short duration to accomplish a modest amount of work. The amount of work involved is, of course, relative and may, as in the instance of driving fasteners into concrete, involve instantaneous work rates of over 100 horse power and instantaneous force loadings of several thousand pounds.
The short duration over which such loadings occur satisfy two fundamental principles. First, the overall energy requirement is relatively modest and the accelerations are very large. The latter point enables a relatively light, portable tool to be essentially unmoved by interface loadings of greater than a thousand pounds as a result of the inertia of the tool mass.
For the most part, heavy duty impact tools are operated by compressed air. Particularly in commercial and industrial settings, such relatively high-energy impact tools require a compressor and a source of compressed air. Despite the need for providing compressors, the efficiency and convenience of impact tools have prompted use on even relatively remote construction jobs by means of portable compressors.
Relatively low energy impact tools, such as lightweight staple drivers, operate on a somewhat different principle. Instead of a constant, high-energy source such as compressed air, a spring is hand compressed to store energy and, again in a short time, released to substantially instantaneously apply the accumulated energy to a ram which, in turn, drives a relatively small staple or nail. Portability is found with high energy in conjunction with the use of discrete charges such as blank cartridges or caseless explosive pellets. However, these are not suitable for high volume, rapid rate work such as is provided by compressor-driven impact tools. U.S. Pat. No. 3,162,123 is illustrative of such prior concepts.
Summarily, other than relatively recent work utilizing fly wheel energy, almost every high-energy impact tool currently used utilizes compressed air and an external substantial power supply as an energy source. In any event, external power sources are required unless a limited supply of discrete charges are employed.